Present methods of blast cleaning utilize a centrifugal throwing wheel for projecting abrasive particles, the particles being subjected to a pre-acceleration action before they are deposited on the inner ends of the blades in the throwing wheel. In some cases, a mechanically driven impeller feeds the abrasive particles to the inner ends of the impeller blades. In other cases, the particles are entrained in a moving stream of air which accelerates the particles prior to depositing them on the inner ends of the blades. In both cases, energy is required to achieve pre-acceleration of the particles and the wear of parts caused by the accelerated particles makes it difficult to control the blast pattern of the impelled particles on the work that is being processed.
It is an object of the present invention, therefore, to provide improved centrifugal blasting apparatus which is simple in construction, requires no moving parts for moving the particles onto the inlet ends of the impeller blades, and provides an improved control of the blast pattern which enables a confined and distinct blast pattern to be maintained during a prolonged service life of the apparatus.